Update docs and examples to batch/v1 Job

Documented manualSelector field. Documented that you do not need to provide a selector or unique labels with batch/v1 Job. Updated all Job examples to apiVersion: batch/v1 Updated all Job examples to use generated selectors.
gmarek · Feb 25, 2016 · 095a85e · 095a85e
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diff --git a/docs/user-guide/job.yaml b/docs/user-guide/job.yaml
@@ -1,16 +1,11 @@
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: pi
 spec:
-  selector:
-    matchLabels:
-      app: pi
   template:
     metadata:
       name: pi
-      labels:
-        app: pi
     spec:
       containers:
       - name: pi

diff --git a/docs/user-guide/jobs.md b/docs/user-guide/jobs.md
@@ -47,6 +47,8 @@ Documentation for other releases can be found at
       - [Controlling Parallelism](#controlling-parallelism)
   - [Handling Pod and Container Failures](#handling-pod-and-container-failures)
   - [Job Patterns](#job-patterns)
+  - [Advanced Usage](#advanced-usage)
+    - [Specifying your own pod selector](#specifying-your-own-pod-selector)
   - [Alternatives](#alternatives)
     - [Bare Pods](#bare-pods)
     - [Replication Controller](#replication-controller)
@@ -76,19 +78,14 @@ It takes around 10s to complete.
 <!-- BEGIN MUNGE: EXAMPLE job.yaml -->
 
 ```yaml
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: pi
 spec:
-  selector:
-    matchLabels:
-      app: pi
   template:
     metadata:
       name: pi
-      labels:
-        app: pi
     spec:
       containers:
       - name: pi
@@ -170,21 +167,9 @@ Only a [`RestartPolicy`](pod-states.md) equal to `Never` or `OnFailure` are allo
 
 ### Pod Selector
 
-The `.spec.selector` field is a label query over a set of pods.
-
-The `spec.selector` is an object consisting of two fields:
-* `matchLabels` - works the same as the `.spec.selector` of a [ReplicationController](replication-controller.md)
-* `matchExpressions` - allows to build more sophisticated selectors by specifying key,
-  list of values and an operator that relates the key and values.
-
-When the two are specified the result is ANDed.
+The `.spec.selector` field is optional.  In almost all cases you should not specify it.
+See section [specifying your own pod selector](#specifying-your-own-pod-selector).
 
-If `.spec.selector` is unspecified, `.spec.selector.matchLabels` will be defaulted to
-`.spec.template.metadata.labels`.
-
-Also you should not normally create any pods whose labels match this selector, either directly,
-via another Job, or via another controller such as ReplicationController.  Otherwise, the Job will
-think that those pods were created by it.  Kubernetes will not stop you from doing this.
 
 ### Parallel Jobs
 
@@ -323,6 +308,70 @@ Here, `W` is the number of work items.
 | Single Job with Static Work Assignment                                     |          W          |        any           |
 
 
+## Advanced Usage
+
+### Specifying your own pod selector
+
+Normally, when you create a job object, you do not specify `spec.selector`.
+The system defaulting logic adds this field when the job is created.
+It picks a selector value that will not overlap with any other jobs.
+
+However, in some cases, you might need to override this automatically set selector.
+To do this, you can specify the `spec.selector` of the job.
+
+Be very careful when doing this.  If you specify a label selector which is not
+unique to the pods of that job, and which matches unrelated pods, then pods of the unrelated
+job may be deleted, or this job may count other pods as completing it, or one or both
+of the jobs may refuse to create pods or run to completion.  If a non-unique selector is
+chosen, then other controllers (e.g. ReplicationController) and their pods may behave
+in unpredicatable ways too.  Kubernetes will not stop you from making a mistake when
+specifying `spec.selector`.
+
+Here is an example of a case when you might want to use this feature.
+
+Say job `old` is already running.  You want existing pods
+to keep running, but you want the rest of the pods it creates
+to use a different pod template and for the job to have a new name.
+You cannot update the job because these fields are not updatable.
+Therefore, you delete job `old` but leave its pods
+running, using `kubectl delete jobs/old-one --cascade=false`.
+Before deleting it, you make a note of what selector it uses:
+
+```
+kind: Job
+metadata:
+  name: old
+  ...
+spec:
+  selector:
+    matchLabels:
+      job-uid: a8f3d00d-c6d2-11e5-9f87-42010af00002
+  ...
+```
+
+Then you create a new job with name `new` and you explicitly specify the same selector.
+Since the existing pods have label `job-uid=a8f3d00d-c6d2-11e5-9f87-42010af00002`,
+they are controlled by job `new` as well.
+
+You need to specify `manualSelector: true` in the new job since you are not using
+the selector that the system normally generates for you automatically.
+
+```
+kind: Job
+metadata:
+  name: new
+  ...
+spec:
+  manualSelector: true
+  selector:
+    matchLabels:
+      job-uid: a8f3d00d-c6d2-11e5-9f87-42010af00002
+  ...
+```
+
+The new Job itself will have a different uid from `a8f3d00d-c6d2-11e5-9f87-42010af00002`.  Setting
+`manualSelector: true` tells the system to that you know what you are doing and to allow this
+mismatch.
 
 ## Alternatives
 

diff --git a/examples/job/expansions/README.md b/examples/job/expansions/README.md
@@ -40,21 +40,18 @@ First, create a template of a Job object:
 <!-- BEGIN MUNGE: EXAMPLE job.yaml.txt -->
 
 ```
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: process-item-$ITEM
+  labels:
+    jobgroup: jobexample
 spec:
-  selector:
-    matchLabels:
-      app: jobexample
-      item: $ITEM
   template:
     metadata:
       name: jobexample
       labels:
-        app: jobexample
-        item: $ITEM
+        jobgroup: jobexample
     spec:
       containers:
       - name: c
@@ -75,12 +72,14 @@ In a real use case, the processing would be some substantial computation, such a
 of a movie, or processing a range of rows in a database.  The "$ITEM" parameter would specify for
 example, the frame number or the row range.
 
-This Job has two labels. The first label, `app=jobexample`, distinguishes this group of jobs from
-other groups of jobs (these are not shown, but there might be other ones).  This label
-makes it convenient to operate on all the jobs in the group at once.  The second label, with
-key `item`, distinguishes individual jobs in the group.  Each Job object needs to have
-a unique label that no other job has.  This is it.
-Neither of these label keys are special to kubernetes -- you can pick your own label scheme.
+This Job and its Pod template have a label: `jobgroup=jobexample`.  There is nothing special
+to the system about this label.  This label
+makes it convenient to operate on all the jobs in this group at once.
+We also put the same label on the pod template so that we can check on all Pods of these Jobs
+with a single command.
+After the job is created, the system will add more labels that distinguish one Job's pods
+from another Job's pods.
+Note that the label key `jobgroup` is not special to Kubernetes. you can pick your own label scheme.
 
 Next, expand the template into multiple files, one for each item to be processed.
 
@@ -113,27 +112,25 @@ job "process-item-cherry" created
 Now, check on the jobs:
 
 ```console
-$ kubectl get jobs -l app=jobexample -L item
-JOB                   CONTAINER(S)   IMAGE(S)   SELECTOR                               SUCCESSFUL ITEM
-process-item-apple    c              busybox    app in (jobexample),item in (apple)    1          apple
-process-item-banana   c              busybox    app in (jobexample),item in (banana)   1          banana
-process-item-cherry   c              busybox    app in (jobexample),item in (cherry)   1          cherry
+$ kubectl get jobs -l app=jobexample
+JOB                   CONTAINER(S)   IMAGE(S)   SELECTOR                               SUCCESSFUL
+process-item-apple    c              busybox    app in (jobexample),item in (apple)    1
+process-item-banana   c              busybox    app in (jobexample),item in (banana)   1
+process-item-cherry   c              busybox    app in (jobexample),item in (cherry)   1
 ```
 
 Here we use the `-l` option to select all jobs that are part of this
 group of jobs.  (There might be other unrelated jobs in the system that we
 do not care to see.)
 
-The `-L` option adds an extra column with just the `item` label value.
-
 We can check on the pods as well using the same label selector:
 
 ```console
-$ kubectl get pods -l app=jobexample -L item
-NAME                        READY     STATUS      RESTARTS   AGE       ITEM
-process-item-apple-kixwv    0/1       Completed   0          4m        apple
-process-item-banana-wrsf7   0/1       Completed   0          4m        banana
-process-item-cherry-dnfu9   0/1       Completed   0          4m        cherry
+$ kubectl get pods -l app=jobexample
+NAME                        READY     STATUS      RESTARTS   AGE
+process-item-apple-kixwv    0/1       Completed   0          4m 
+process-item-banana-wrsf7   0/1       Completed   0          4m 
+process-item-cherry-dnfu9   0/1       Completed   0          4m 
 ```
 
 There is not a single command to check on the output of all jobs at once,
@@ -170,21 +167,17 @@ First, download or paste the following template file to a file called `job.yaml.
 {%- for p in params %}
 {%- set name = p["name"] %}
 {%- set url = p["url"] %}
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: jobexample-{{ name }}
+  labels:
+    jobgroup: jobexample
 spec:
-  selector:
-    matchLabels:
-      app: jobexample
-      item: {{ name }}
   template:
-    metadata:
       name: jobexample
       labels:
-        app: jobexample
-        item: {{ name }}
+        jobgroup: jobexample
     spec:
       containers:
       - name: c

diff --git a/examples/job/expansions/job.yaml.jinja2 b/examples/job/expansions/job.yaml.jinja2
@@ -5,21 +5,17 @@
 {%- for p in params %}
 {%- set name = p["name"] %}
 {%- set url = p["url"] %}
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: jobexample-{{ name }}
+  labels:
+    jobgroup: jobexample
 spec:
-  selector:
-    matchLabels:
-      app: jobexample
-      item: {{ name }}
   template:
-    metadata:
       name: jobexample
       labels:
-        app: jobexample
-        item: {{ name }}
+        jobgroup: jobexample
     spec:
       containers:
       - name: c

diff --git a/examples/job/expansions/job.yaml.txt b/examples/job/expansions/job.yaml.txt
@@ -1,18 +1,15 @@
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: process-item-$ITEM
+  labels:
+    jobgroup: jobexample
 spec:
-  selector:
-    matchLabels:
-      app: jobexample
-      item: $ITEM
   template:
     metadata:
       name: jobexample
       labels:
-        app: jobexample
-        item: $ITEM
+        jobgroup: jobexample
     spec:
       containers:
       - name: c

diff --git a/examples/job/work-queue-1/README.md b/examples/job/work-queue-1/README.md
@@ -262,21 +262,16 @@ image to match the name you used, and call it `./job.yaml`.
 <!-- BEGIN MUNGE: EXAMPLE job.yaml -->
 
 ```yaml
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: job-wq-1
 spec:
-  selector:
-    matchLabels:
-      app: job-wq-1
   completions: 8
   parallelism: 2
   template:
     metadata:
       name: job-wq-1
-      labels:
-        app: job-wq-1
     spec:
       containers:
       - name: c

diff --git a/examples/job/work-queue-1/job.yaml b/examples/job/work-queue-1/job.yaml
@@ -1,18 +1,13 @@
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: job-wq-1
 spec:
-  selector:
-    matchLabels:
-      app: job-wq-1
   completions: 8
   parallelism: 2
   template:
     metadata:
       name: job-wq-1
-      labels:
-        app: job-wq-1
     spec:
       containers:
       - name: c

diff --git a/examples/job/work-queue-2/README.md b/examples/job/work-queue-2/README.md
@@ -217,20 +217,15 @@ Here is the job definition:
 <!-- BEGIN MUNGE: EXAMPLE job.yaml -->
 
 ```yaml
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: job-wq-2
 spec:
-  selector:
-    matchLabels:
-      app: job-wq-2
   parallelism: 2
   template:
     metadata:
       name: job-wq-2
-      labels:
-        app: job-wq-2
     spec:
       containers:
       - name: c

diff --git a/examples/job/work-queue-2/job.yaml b/examples/job/work-queue-2/job.yaml
@@ -1,17 +1,12 @@
-apiVersion: extensions/v1beta1
+apiVersion: batch/v1
 kind: Job
 metadata:
   name: job-wq-2
 spec:
-  selector:
-    matchLabels:
-      app: job-wq-2
   parallelism: 2
   template:
     metadata:
       name: job-wq-2
-      labels:
-        app: job-wq-2
     spec:
       containers:
       - name: c